–First
time artificial and biological neurons function together in a network
family–

An interdisciplinary group
of scientists at the University of California, San Diego has teamed up
in a unique experiment that may eventually lead to restoring brain
function in patients suffering from stroke, Alzheimer’s and other
neurological disfunctions.

The team of researchers at
UCSD’s Institute for Nonlinear Science (INLS) led by Henry Abarbanel,
professor of physics, Misha Rabinovich at INLS and Allen Selverston,
professor emeritus of biology, has successfully integrated an
electronic neuron within a group of 14 biological neurons from the
California spiny lobster. The artificial neuron was accepted by the
real ones and its signaling rhythm fell into place with the other
cells.

“We built an electronic
neuron that is able to work as a member of a neural framework,” said
Abarbanel, director of INLS. “It’s science fiction, except that we
did it.”

The finding comes after
two years of research, using $7.50 worth of circuit parts from a Radio
Shack store and dozens of spiny lobsters from La Jolla Cove purchased
from a local fisherman.

It is the first time that
researchers have been able to get artificial and biological neurons to
function together in a network family. In their normal function, the
14 neurons control the rhythmic way food is passed from the stomach to
the lobster’s digestive system.

The researchers said the
key finding was in the mathematical modeling that preceded the actual
experiment. They discovered that they only need to control three
variables that affect a neuron’s overall function, rather than the
hundreds of variables involved in the detailed biological functioning
of each cell. This finding radically simplified the mathematical
algorithm used to construct the circuit.

“We found a way to
replace the neuron without getting lost in the details,” said
neuroscience researcher Rob Elson. “It’s a higher level of
modeling where you capture the performance according to a model
involving a few variables, and you’re not concerned directly with
all the small cogs working behind the scenes.”

The model used to describe
the neuron’s function was so simple that it was done on a desktop
personal computer, and was then used to construct an inexpensive
circuit built from mail-order parts.

The researchers chose the
California spiny lobster because it is a well-studied animal model.
The 14 neurons are highly interconnected and capable of complex
control processes. Like other neurons, they oscillate in both a slow
and a fast way using the fast oscillations to send signals between
neurons through their axons.

The group of lobster
neurons, called the central pattern generator, performs regular
oscillations so the lobster’s food is passed efficiently to its
digestive system.

By removing crucial
biological neurons from the natural circuit, the UCSD researchers
created an unhealthy state of oscillations in the neurons, added the
electronic one, and were able to get the entire network to return to
its normal state.

“We’ve created lobster
‘epilepsy’ and then cured it,” Abarbanel said.

The next step is to
gradually replace each of the neurons with electronic ones. If the
entire network still functions properly, the researchers will be
closer to replacing diseased or damaged neurons in human tissue. The
UCSD researchers see their work as having important impacts on spinal
cord research, for example.

The
team working on the two-year project includes Abarbanel, Rabinovich,
Selverston, Elson, and postdoctoral fellows Pablo Varona, Alexander
Volkovskii and Atilla Szucs.